1. Field of the Invention
The present invention relates to a curved lens combination for swimming/diving goggles that has no refraction power change when used in water, provides improved safety, and reduces water resistance.
2. Description of the Related Art
A swimmer or diver often wears a pair of goggles to obtain a good view in addition to protection to his/her eyes. FIG. 11 of the drawings illustrates a pair of conventional swimming goggles 2' that provides close contact with the user's eye sockets to keep the eyes 1' away from water. The lens 3' is substantially planar at both sides thereof without causing refraction of light passing therethrough. An outer surface of the lens 3' contacts with water and an inner surface of the lens 3' contacts with air. The light from an object in water passes through air inside the swimming goggles 2' into the user's eye such that clear image may be properly formed on the user's retina 11'. Namely, the lens 3' does not incur any refraction power change when placed in air or in water such that the image of object can be clearly formed on the user's retina.
Curved lens is used to replace planar lens, as the latter fails to provide aesthetically pleasing effect and increases water resistance. FIG. 12 illustrates a typical curved lens 6' including a spherical outer surface 61' with a refraction power of, e.g., +3 diopters, and a spherical inner surface 62' with a corresponding refraction power of, e.g., -3 diopters. Thus, when in air, the overall optical effect for the light passing through the outer surface 61' and the inner surface 62' is zero. Namely, no refraction power change is incurred. Nevertheless, when in water, the outer surface 61' of the lens 6' contact with water 4' that has a refraction rate of 1.33 and the inner surface 62' of the lens 6' contacts with air 5' that has a refraction rate of 1. In addition. the curved outer surface 61' and the water 4' between the object and the lens 6' together form a concave lens (see the dashed lines). This results in a change in the light-curving rate (i.e., the light-curving rate is not equal to three), yet the light-curving rate from the inner surface 62' to the air 5' still remains unchanged (equal to three). As a result, the image of the object in water formed on the user's retina 11' is smaller than the object. Namely, the so-called refraction power change occurs. This problem is aggravated if the outer surface 61' of the lens 6' has a larger curvature.
The present invention is intended to provide a curved lens combination for swimming/diving that mitigates and/or obviate the above problems.